Path having variable resistance to vehicles moving on it

ABSTRACT

A runway or landing surface for vehicles and particularly aircraft, such surface including a casing or enclosure containing granular material, the casing being connected to means for producing a vacuum within it to an extent to cause compaction of the granular material in order to produce a hard landing surface, and means for breaking or reducing the vacuum or its effect when a soft surface is desired to thereby result in resistance to forward movement of the aircraft or other vehicle.

I Umted States Patent 1 3,659,812 Carlsson May 2, 197 2 PATH HAVING VARIABLE [56] References Cited gfisllgrmca T0 VEHICLES MOVING UNITED STATES PATENTS 3,066,896 12/1962 Schirtzinger ..244/ i 14 R [72] inventor: Sixten Einar Carlsson, Norrkoping, FOREIGN PATENTS OR APPLICATIONS Swde" 742,240 12/1955 Great Britain ..244/114 R [73] Assignee: Borgs Febrile; AB, Norrkoping, Sweden Primary Examiner-Milton Buchler Flledi p 24, 1970 Assistant Examiner-Paul E. Sauberer pp 75 168 Attorney-Munson8z Fiddler [57] ABSTRACT A runway or landing surface for vehicles and particularly air- [30] Foreign Application Priomy Dam craft, such surface including a casing or enclosure containing Dec. 1, 1969 Sweden ..l6482/69 granular material, the casing being connected to means for c a .r a producing a vacuum within it to an extent to cause compaction of the granular material in order to produce a hard land- [52] US. Cl. ..244/ll4 R, 94/7 i u fa e, and means for breaking or reducing the vacuum [51] Int. Cl. ..B64f 1/02 or its effect when a soft surface is desired to thereby result in [58] Field of Search ..244/1 14 R, 110 A; 94/27, 7, resistance'to forward movement of the aircraft or other vehi- 8 Claims, 4 Drawing Figures J L J g 3 Patented May 2, 1972 S IKTLH ii INAR CAHLSSOH INVENTOR MUNSON 6 PATH HAVING VARIABLE RESISTANCE TO VEHICLES MOVING ON IT BACKGROUND OF THE INVENTION The present invention is adapted for use in connection with within a relatively short distance, Generally, there are two difl 5 ferent kinds of aircraft arresting means. One of these is the net barrier, the aircraft being caught in a net, which folds itself around the aircraft, the braking effect being achieved by means of energy-absorbing devices connected to both ends of the net. A second type includes an arrester hook on the air- 2 craft, which catches in a steel wire stretched transversely across the landing path. The hook carried by the aircraft, engages the wire, the ends of the wire being connected to energy-absorbing devices.

Both of these barriers have certain advantages and disadvantages. One advantage afforded by the net barrier isthat the. aircraft need not be provided with an arresterhook, thereby saving considerable weight as compared to an aircraft pro,- vided with a hook. On the other hand, the barrier net makes possible certain fonns of damage to the aircraft when arresting 30.

the movement thereof. This often results in expensive repair work. As distinguished from this, the arrester hook has an advantage whereby damage is not often caused to the aircraft, although it does possess the disadvantage whereby the weight of the aircraft is increased. This is a serious disadvantage both with respect to military and to civil aircraft. A further disadvantage of the net barrier is that it is only suited to jet propelled aircraft since aircraft provided with propellers cannot, in principle, use the net barrier.

The present invention has all of the advantages of the forementioned types of aircraft barriers and lacks their disadvantages. The arrangement of the present invention requires no special equipment to be installed on or in the aircraft. No damage is caused to an aircraft when arrested by the meansof the invention, and said means is both suited for jet propelled and propeller aircraft. Furthermore, the invention provides calculated braking assistance for aircraft which vary widely in weight and undercarriage geometry, whereby braking is neither too abrupt nor too gentle.

The invention is based on a physical phenomonen which occurs when a particular material such as a granular material is enclosed in a sealed and flexible casing, in whichdifferent degrees of vacuum can prevail. In the absence of a vacuum,

that is when there is no pressure difference between the inside 5 5 and outside surfaces of the basing, the filling material has full freedom of movement, while if there exists a difference of pressure across the casing wall so that the pressure on the inside is lower than the pressure on the outside, the flexible wall of the casing compacts the granular material enclosed in the 0 casing, thereby limiting its freedom of movement proportionally to the difference in pressure in a manner, in the case of a high vacuum, the granules are practically unable to move at all. This physical effect is caused by the fact that when the casing is compressed as a result of the vacuum, the. granules are urged together in a manner whereby the friction acting between them prevents them from moving.

A system based on this physical effect and the casing of which has a width generally equal to the width of the runway or path and presents a smoothupper surface whereby the casing forms a smooth continuation of the runway proper, obtains whensubjected to a high degree of vacuum, that is, up to l atmosphere pressure difference, a degree of hardness in the same order of hardness as that of the runway, thereby permitting aircraft and other vehicles to move along the same exactly as though they were moving on the actual runway. If, however, atmospheric air is allowed to enter the casing, the pressure difference is reduced and therefore the force compacting the granules, whereby the granules are able to move more easily and the surface becomes softer, which means that the wheels of the aircraft or vehicle deform the casing to a corresponding degree, thereby causing an increased resistance to rolling.

In the absence of any pressure difference whatsoever, and with a fully flexible casing wall, the effect is essentially the same as if the wheels were moving in the filling material itself, the result is a radically increased tractive resistance, and tests have shown that the resulting increase in retardation of the aircraft or other vehicle over and above that provided by its own braking system is of the order of 8-12 m/sec with suitable filling material, suitable casing material and at the specific wheel pressure common with aircraft, for example.

DESCRIPTION In the accompanying drawing, wherein an illustrative embodiment of the invention is disclosed,

FIG. 1 shows a portion of a path or runway in longitudinal section and in which the'invention is embodied;

FIG. 2 is a cross-sectional view taken substantially on the line II-ll of FIG. 1;

FIG. 3 is a perspective view of a portion of the casing, and

FIG. 4 is a diagrammatic view showing a vacuum means for the system.

In connection with and beneath appropriate longitudinal portions of a conventional path or runway I is arranged a sunken foundation or depression formed by a supporting surface 2, which together with side-defining surfaces or walls 2 and a covering comprising a flexible mat 4, form a hermetically sealed casing or chamber having the same width as the width of the normal path or runway, and. presenting a flat upper surface. The initial portion of the sunken foundation 2 is inclined and merges gradually with the normal path I. Enclosed in. the casing or chamber thus formed is a granular filling material 3. Such. material may consist of sand, gravel or any other suitable hard. granular material.

In FIG. 3-.is shown how the flexible mat or covering 4 can be formed. The basic material for the mat can be for example, rubber or plastic material 4 reinforced with a network or mesh of steel wire 4 in a manner whereby flexibility of the basic material of the mat is retained.

FIG. 4 illustrates diagrammatically a system of conduits 6 connected to the closed casing at a suitable number of points distributed over the bottom surface of the casing, filters or strainers 11 being provided to prevent the granular material from entering the conduits. One or more vacuum pumps 7 are connected to the system for evacuating the casing. Also connected in the conduit system 6 is a valve means 8, adapted to close the system from atmospheric air and which is controlled by asignal operating through a line 9, to open the conduit system 6 during certain periods, through an air intake 10, in a manner by which the degree of vacuum in the casing can be reduced to a value corresponding to the operating signal.

In .FIGS. 1 and 2 is shown how the covering mat 4 has arranged at a suitable number of points over its surface, flexible connections 5, joining the mat to the sunken foundation or base 2, for the purpose of preventing excessive horizontal movement of the mat .while retaining a certain freedom of vertical movement.

The operation of the-described invention is substantially as follows:

Normally, all air.is evacuated from the casing, and hence the top surface of the same is smooth and is very hard. Aircraft are therefore able torun unhindered on the upper surface of the casingason a mat, without the casing being deformed. Aircraft are even able. to land, that is, settle with their wheels on the surface, without any negative effect. Located in the vacuum system which has previously evacuated the air from the casing are regulable valves which pennit air to enter the casing during certain, predetermined periods of time. The time periods are determined by the different parameters of the aircraft such as the weight of the aircraft, the normal lift coefficient of the aircraft in its moving attitude and the geometry of the undercarriage. when a critical situation seems apparent, that is when there is a risk that an aircraft will not be able to stop within the runway space available under its own braking system, the regulating valves are opened upon a signal from air traffic control for that period of time which provides a degree of vacuum corresponding to the combination of the forementioned aircraft constants. This provides the system with a degree of softness which results in an increased tractive resistance of such magnitude that maximum braking assistance is given, without increasing said resistance to such an extent that there is danger of a ground accident.

What is claimed is:

l. A system for use with paths used by aircraft or other vehicles whereby, when desired, a braking effect can be exerted in addition to the braking effect obtained with the usual braking system of the vehicle, the path having a surface material such as sand, grave] or similar granular material enclosed in a hermetically sealed enclosure; said enclosure being connected to vacuum-producing means by which the enclosure is air-evacuated when a firm surface is required, the material being then compacted and becoming solid, and when an increased resistance to rolling is desired the vacuum is broken so that the material becomes deformable.

2. A system according to claim 1, wherein the surface material is contained in a recess in the path, the casing consisting of walls of the recess and with a mat covering the walls and the surface material.

3. A system according to claim 2, wherein the mat comprises flexible material such as rubber or plastic reinforced with a material of high mechanical strength, said reinforcement being made flexible by being formed of a steel wire network structure.

4. A system according to claim 1, wherein the upper portion of the casing situated in the plane of the path is connected at a number of positions with underlying stationary portions of the path by means of flexible connecting means of such length that horizontal movement of the upper path portion is restricted.

5. A system according to claim 2, wherein the recess is located in a path of known construction and in a manner whereby the bottom of the recess is connected to the path by a sloping bottom portion.

6. A system according to claim 1, wherein a system of conduits connects with the casing and vacuum pumps, the conduits being provided with shut-off valves.

7, A system according to claim 6, wherein, in addition to the shut-off valves, the conduit system is also provided with valves for regulating the entry of atmospheric air into the casing so that, when required, a lower degree of vacuum can be immediately obtained.

8. An aircraft runway having a depression provided with a bottom surface, a covering composed of a reinforced flexible material above the depression, the covering and bottom surface defining a closed space containing a granular material, means for creating a vacuum is said space to result in compaction of the granular material and produce a hard surface for a vehicle to traverse, and means for reducing the vacuum to soften said surface and produce tractive resistance to a vehicle passing over it. 

1. A system for use with paths used by aircraft or other vehicles whereby, when desired, a braking effect can be exerted in addition to the braking effect obtained with the usual braking system of the vehicle, the path having a surface material such as sand, gravel or similar granular material enclosed in a hermetically sealed enclosure; said enclosure being connected to vacuum-producing means by which the enclosure is air-evacuated when a firm surface is required, the material being then compacted and becoming solid, and when an increased resistance to rolling is desired the vacuum is broken so that the material becomes deformable.
 2. A system according to claim 1, wherein the surface material is contained in a recess in the path, the casing consisting of walls of the recess and with a mat covering the walls and the surface material.
 3. A system according to claim 2, wherein the mat comprises flexible material such as rubber or plastic reinforced with a material of high mechanical strength, said reinforcement being made flexible by being formed of a steel wire network structure.
 4. A system according to claim 1, wherein the upper portion of the casing situated in the plane of the path is connected at a number of positions with underlying stationary portions of the path by means of flexible connecting means of such length that horizontal movement of the upper path portion is restricted.
 5. A system according to claim 2, wherein the recess is located in a path of known construction and in a manner whereby the bottom of the recess is connected to the path by a sloping bottom portion.
 6. A system according to claim 1, wherein a system of conduits connects with the casing and vacuum pumps, the conduits being provided with shut-off valves.
 7. A system according to claim 6, wherein, in addition to the shut-off valves, the conduit system is Also provided with valves for regulating the entry of atmospheric air into the casing so that, when required, a lower degree of vacuum can be immediately obtained.
 8. An aircraft runway having a depression provided with a bottom surface, a covering composed of a reinforced flexible material above the depression, the covering and bottom surface defining a closed space containing a granular material, means for creating a vacuum is said space to result in compaction of the granular material and produce a hard surface for a vehicle to traverse, and means for reducing the vacuum to soften said surface and produce tractive resistance to a vehicle passing over it. 